Method of burning fuel



Oct. 20, 1936.

E. G. BAILEY METHOD OF BURNING FUEL ori in-a1 Filed May 2, 192a 2 silegts-sheefl" Oct. 20, 1936. E. e. BAILEY METHOD OF BURNING FUEL Original Filed May 2,, 1928 2 Sheets-Sheet 2' INVENTOR QTRVl/Y CI Bil/LEV TRE Patented Oct. 20, 1936 PATENT OFFICE Mn'rnon F BURNING FUEL Ervin G. Bailey, Easton, Pa, assignor, by mesne assignments, to The Babcock & Wilcox Company, Newark, N. J., a corporation of New Jersey Continuation of application Serial No. 274,535,

2, 1928. This application November 3,

1931, Serial No. 572,778

My invention relates to a method of burning fuel in a furnace, and is particularly useful in connection with pulverized coal. The present application is a continuation of my copending application for "Method of burning fuel, filed May 2, 1928 and serially numbered 274,535.

Among the objects of the invention may be mentioned employing radiant heat from the furnace floor to assist in combustion of fuel entering the furnace, the provision of a method of burning fuel whereby a pool of molten material may effectively coact with the entering fuel stream to assist in the propagation of the flame, and employing the heat of the burning fuel to keep the slag in the bottom of the furnace molten. Other objects will be apparent upon consideration of,

the present specification.

One form of the invention is shown byway of illustration in the accompanying drawings in which- Figure 1 is avertical section through a furnace and boiler, the apparatus being adapted for use in accordance with the invention, and

Fig. 2 is a horizontal section on the line II'II in Figure 1. g The invention is illustrated in its application to a furnace disposed beneath a boiler of known type, which comprises a plurality of water tubes i connecting downtake headers 2 and uptake headers 3, respectively. Steam generated from the water in the tubes passes to a cross-drum I and thence to a superheater 5, all in well known manner.

Beneath the boiler there is shown a furnace 35 which is illustrated as being substantially square in form,- although clearly other forms may be employed in connection with the invention. The furnace walls are shown as formed of water tubes 8 connected to the water circulating system of the 40 boiler in the usual manner.' Blocks I are carried by the tubes to complete the furnace wall.

A burner 8 adapted to project streams of mixed fuel and air is shown in each wall. Although the burner employed may be one which may be used with any desired type of fluid fuel, for purposes of illustration reference will be made to pulverized coal, and burners adapted to burn pulverized coal are shown in the drawings. Each of the burners is of a form which will cause turbulence in the 0 fuel stream at the mouth of the burner where the stream enters the furnace.

In the type of burner illustrated, primary air and pulverized coal are admitted to the furnace through a nozzle 9 having an elongated opening therein with the long dimension arranged vertically in the furnace wall. On opposite sides of the nozzle opening air-ports Iii are provided, which air-portsare staggered along the vertical extent of the burner opening, as best illustrated in Figure 1. Secondary air entering the furnace from these ports therefore, impinges upon the sides of the fuel stream as it leaves the nozzle 9'.

In order to overcome a tendency toward stratification of the fuel and secondary air, which is particularly marked in large furnaces, the burners are preferably arranged so that each stream of fuel is directed against another stream of fuel, as diagrammatically illustrated in ,Fig. 2. .Where this is done, a second turbulence is effected which breaks up any stratification, although combustion is largely completed because of the turbulence at the burner opening, the second turbulence in a. zone of high temperature resulting from impingement of one fuel stream upon another causes sub stantially complete combustion.

The combustion is particularly aided by the fact that the burners are disposed near the fioor of the furnace. The floor thus becomes heated to a high degree, and the heat in the floor radiates the direction of flow of the several fuel streams and the proximity thereof to the slag pool, the relatively hot slag beneath the hotter central zone of second turbulence is moved to the outside and beneath the burners. As shown in Fig. 2, the general direction of movement of the burning fuel streams is counter-clockwise. Such a movement, in view of the proximity of the streams to the pool will necessarily came the relatively thin hot slag on the surface of the pool to also move in a counter-clockwise direction. The action is similar to the movement of water due to air currents flowing over the surface thereof.

For the collection of slag separated in the furnace, I provide a floor structure having an upper layer of suitable material ll upon which the slag accumulates. 'The slag is then maintained in a liquid pool on the floor of the furnace and tapped off from time to time through a suitable tapping spout II. A particular method of maintaining the slag pool and the furnace wall and floor structure forming the boundaries of the pool and of removing the slag from the pool is disclosed and claimed in my prior Patent 1,986,663, granted Jan. 1, 1935.

By providing turbulent burners located near the slag tap floor, the heat of the burning fuel from these burners acts to keep the slag in the bottom of the furnace in a molten state. Radiant heat from this molten slag in turn assists in the propagation of the flame. It will be observed that the combustion zone, together with the slag bottom, are a considerable distance below the heat absorbing surface of the boiler. As a result this heat absorbing surface does not have a chilling effect upon the slag.

The details here illustrated and particularly described are presented merely as examples of how the invention may be applied and are not intended to be construed as limitations. With this understanding- I claim 1. In a method of burning fuel in a furnace chamber having a heat resistant bottom for supporting a slag pool, the steps which comprise collecting and maintaining molten slag in a pool of substantial depth over the furnace bottom; introducing separate streams of finely divided fuel into the lower portion of the chamber in approximately opposing relatively offset relation to one another and with sufficient air in each stream for supporting combustion of the fuel therein; separately mixing the fuel and air of each stream as it enters the chamber; igniting the fuel of each stream as it enters the chamber by heat from previously ignited fuel and from the slag pool therebeneath; and then mixing the burning fuel and air of all streams in a zone adjacent the center of the chamber.

2. In a method of burning fuel in a furnace chamber having a heat resistant bottom for supporting a slag pool, the steps which comprise collecting and maintaining molten slag in a pool of substantial depth over the bottom; introducing separate streams of finely divided fuel into the lower portion of the chamber in approximately opposing relatively offset relation to one another and with suflicient air in each stream for supporting combustion of the fuel therein: separately mixing the fuel and air of each stream as it enters the chamber; igniting the fuel of each stream by heat from previously ignited fuel and from the slag pool therebeneath; constantly moving the relatively hot slag in the pool to points beneath the entering fuel streams to increase the temperature of the chamber at such points and thereby aid still further in the early distillation and ignition of the fuel; and then mixing the burning fuel and air of all streams in a zone adjacent the center of the chamber.

3. In a method of burning fuel in a furnace chamber having a heat resistant bottom for supporting a slag pool, the steps which comprise collecting and maintaining molten slag in a pool of substantial depth over the furnace bottdm; introducing separate streams of finely divided fuel with sufficient air in each stream to support combustion of the fuel therein into the lower portion of the chamber in approximately opposing relatively offset relation to one another and with the general direction of adjacent streams at angles of approximately when considered with respect to the vertical center line of the chamber; separately mixing the fuel and air of each stream as it enters the chamber; igniting the fuel of each stream as it enters the chamber by heat from previously ignited fuel and from the slag pool therebeneath; and then mixing the burning fuel and air of all of the streams in a zone adjacent the center of the chamber.

4. In a method of burning fuel in a furnace chamber having a heat resistant bottom for supporting a layer of molten slag, the steps which comprise maintaining molten slag in a layer over the furnace bottom; introducing separate streams of finely divided fuel into the lower portion of v the chamber in approximately opposing relatively offset relation to one another and with suflicient air in each stream for supporting combustion of the fuel therein; separately mixing the fuel and air of each stream as it enters the chamber; igniting the fuel of each stream as it enters the chamber by heat from previously ignited fuel and from the molten slag layer therebeneath; and then mixing the burning fuel and air of all streams in a zone adjacent the center of the chamber.

ERVIN G. BAILEY. I 

